Re: Sharing data directories between machines

On Aug 6, 2013, at 10:45 AM, JD Wong <jdmswong(at)gmail(dot)com> wrote:

> Hi all!
>
> I have two servers, which share a large mounted drive. I would like to share postgres databases between them dynamically so that when one makes changes, they are immediately available in the other.
>
> I tried moving the data directory over to the mounted drive, and pointing both postgresql.confs to that one. I was able to have both access the same databases, but they can't share changes. It's like they're running on two separate data directories, even though show data_directory reports the same path for each.

That'll likely damage your database, probably irrecoverably.

> How can I make them play nicely?

You can't do it by sharing the disk files, at all. The two instances will trash each others data.

If you want multiple database servers for redundancy, or you want to be able to offload read access to a second server, take a look at hot standby servers. http://www.postgresql.org/docs/9.2/static/high-availability.html

If you really want to be able to write to either database and have it replicated to the other one immediately, you should probably rethink what you need. It can be done (with multimaster replication) but it's almost never the right approach.

Cheers,
Steve